There are many known procedures for producing small particles. Such particles find utility in numerous applications including those utilizing magnetic pigments, metallic catalysts, and reinforcing fillers such as, e.g., carbon black and pyrogenic silica.
Some of the more important work in the area of making such small particles was carried out by Ehrreich and Reti and is described in U.S. patent applications Ser. No. 228,387 filed on Feb. 22, 1972, now U.S. Pat. 3,892,673, and Ser. No. 367,461 filed on June 6, 1973, now U.S. Pat. 3,843,349. The Ehrreich-Reti work related to processes involving reduction of organometallic salts to form metal powders of improved magnetic properties. A number of other workers including Haines in U.S. Pat. 3,574,685 and Neel in U.S. Patent 2,651,105 also worked in this field and they, too, were primarily interested in the manufacture of magnetic materials.
Although the Ehrreich-Reti work provided an important advance in the art, there were still some drawbacks associated with the products made by their procedures. The inventions which are described below were made during investigations directed to making improved products according to the Ehrreich-Reti procedures.
Other prior work also is seen to relate to the present invention in view of the discoveries made during the evaluation of the novel products of the invention. This work is that generally relating to the fields of metallic catalysis, reinforcement of resins and polymer materials with reinforcing fillers. In general, problems are encountered in all of these fields providing small particles which meet such parameters as available pores of optimum size, surface area, available wetted surface, or other such requirements of various systems.
Therefore, it has been desirable to provide a versatile process for making powders, especially metal-bearing powders wherein one can achieve very small particles having a wide variety of atomic configurations, a high surface area, and, especially, a high porosity.